The present invention is relating to an electrolyser and to an electrode structure in such electrolyser.
The invention consists also in a method for electrolysing water by using such electrolyser.
The technology of producing hydrogen by the electrolysis of water dates back to the last century. Conventionally the process is accomplished by placing electrodes into a water solution containing electrolyte material (potassium hydroxide or hydrochloric acid). When an appropriate electrical current is passed through the electrodes, oxygen bubbles form on one electrode and hydrogen on the other. Commercial electrolysis equipment has been manufactured utilizing this technology for many years. Recently, researchers have substituted a solid polymer type membrane material between two electrodes thereby making possible the electrolysis of pure water with the advantage of more efficient conversion and lower cell maintenance costs. The solid polymer electrolyte also provides the capability of producing hydrogen at high pressure, thereby eliminating the need for expensive and energy intensive secondary compressors.
Such solid polymer electrolytes (SPE) have been disclosed in following publications : "Solid Electrolytes Offer Route to hydrogen", Chemical and engineering News, Aug. 27, 1973; "Electrolytic Hydrogen fuel Production with Solid Polymer Electrolyte Technology" by W. A. Titterinton and A. P. Fickett, VIII IECEC Proceedings ; and "A Hydrogen-Energy System", published by American Gas Association, 1973. As described in these references, SPE is typically a solid plastic sheet of perfluorinated sulfonic acid polymer which, when saturated with water, becomes an excellent ionic conductor. The ionic conductivity results from the mobility of the hydrogen ions which move through the polymer sheet by passing from one sulfonic acid group to another. An anode and cathode are positioned on either side of the sheet and pressed thereagainst to form the desired SPE cell.
Electrolysis apparatus utilizing such SPE cell are described in U.S. Pat. Nos. 4,056,452 and 4,210,511.
In these patents the anode plates present in one of their sides alternating ridges and grooves. This makes the anode plates costly, as grooves are very expensive to fabricate.
Moreover, especially in the electrolyser of U.S. Pat. No. 4,210,511 so called back-up rings are used for supporting the outer O-rings which are required to seal the outer perimeter of the cathodes and to prevent the escape of hydrogen.
These back-up rings have been traditionally machined out of fiber glass and are thus very expensive.
Moreover, on several occasions they have ruptured while the electrolyser was in use causing severe damage to the cell. In addition, very tight tolerances must be maintained in the fabrication of these back-up rings in order to achieve proper sealing. These tight tolerances on such a large diameter have made the back-up rings one of the most expensive parts of the cell.
It is one of the principal objectives of the present invention to provide an improved electrolyser which is more reliable and less costly than the known electrolysers of the prior art.
A further objective of the invention is to provide an electrolyser which has improved means for supplying liquid to the anode plates and for withdrawing fluid and the products formed at the anode and cathode plates.
A still further objective of the invention is to provide a new method for electrolysis of a liquid consisting of water to produce hydrogen and oxygen therefrom.
Additional objectives are to provide a very compact electrolyser which moreover enables to obtain hydrogen at relative high pressure.